Share-Based Compensation (Details) (USD $) Share data in Thousands, unless otherwise specified	3 Months Ended				6 Months Ended		3 Months Ended		6 Months Ended			6 Months Ended	0 Months Ended		6 Months Ended
	Jun. 28, 2013		Jun. 29, 2012		Jun. 28, 2013	Jun. 29, 2012	Jun. 28, 2013 Stock Options [Member]	Jun. 29, 2012 Stock Options [Member]	Jun. 28, 2013 Stock Options [Member]	Jun. 29, 2012 Stock Options [Member]	Dec. 25, 2009 Stock Options [Member]	Jun. 28, 2013 2013 LTIP [Member]	May 07, 2013 2013 LTIP [Member] Performance Units [Member]	May 07, 2013 2013 LTIP [Member] Restricted Stock Units (RSUs) [Member]	Jun. 28, 2013 2013 LTIP [Member] Minimum [Member]	Jun. 28, 2013 2013 LTIP [Member] Maximum [Member]
Share-based Compensation
Units granted as part of the 2013 LTIP													1,300	439
Percentage Of Grants With Performance Vesting, Operating Ratio													50.00%
Percentage Of Grants With Performance Vesting, Return On Assets													50.00%
Payout percentage of the target awards (percent)															0.00%	200.00%
Maximum downward adjustment to payout percentage												30.00%
Restricted stock vesting period														3 years
Share-Based Compensation Expense	$ 5,000,000	[1]	$ 4,000,000	[1]	$ 2,000,000	$ 4,000,000
Income Tax Benefit	2,000,000		1,000,000		1,000,000	1,000,000
Number of Stock Options Exercised							472	319	1,663	1,618
Number of Stock Options Expired							9	0	9	15
Future expense related to vested options											$ 0
Number of Stock Options Outstanding							0		0

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